Using system call to change oracle instance

[Larry Young <LYoung@CONTINENTAL.COM>]

A question I hope someone can help resolve. I have a number of Oracle
instances on one unix box.  Instead of running my  program a number of
times, I am attempting to change the instance in SQR. So far I have been
unable to change the instance in SQR. Any ideas?   The code is

        call system using 'export ORACLE_SID=ne;'   #SID

When I run this I get the error ORACLE_SID=ne; is not an identifier.

As an fyi I am able to change the oracle instance at the unix prompt
using
        export ORACLE_SID=ne;

Any ideas would be greatly appreciated.  Thanks in advance.